Answer:
1. ☹️
2. ☺
3. ☹️
4. ☺
5. ☺
Explanation:
1. Opaque objects like a thick cardboard do not let light pass through them.
2. Convection is the transfer of heat via gases and liquids.
3. If the lights are placed on the side, the driver cannot see the road in front of him/her nor the drivers following behind him/her.
4. Optical fibers are used to transmit information (communication) and as a component for medical equipment (medicine) and other machinery (industry).
5. Sound travels at varying speeds depending on the medium.